On today's POV Blog, 2014 Fellow Colin Nusbaum is interviewed about the role of the assistant editor:

What are the responsibilities of an assistant editor? Do they vary from job to job, or are they very well defined?

Each film is going to be very different. I’ve rarely ever replicated the exact process as an assistant, but always took it upon myself to carefully consider what might work best given the technicalities and goals for each film. Naturally, that also meant that if an editor was already set to work on the film that I would check in with him or her about organizational preferences.